Rat Problem
by fireworksinthenight
Summary: Bringing home mysterious Kraang devices can't always be a good idea. Now the turtles find themselves in a… predicament. Hopefully Donnie can fix this - and in the meantime, how hard can it be to babysit your own father?
1. Prologue

_AN: One day, I'll manage to convince my brain that you can't take a break from writing turtles by writing turtles. In the meantime, here is a short fic (maybe a few chapters long?) with 2012 turtles somewhere during season 2, and a classic plot...sort of. I don't own the turtles._

 _I'm so not sorry about this._

* * *

 **Prologue**

* * *

The four turtles were lined up in front of their father, telling him with enthusiasm about their last fight – a victory, of course – against the Kraang. The giant rat and powerful ninja master was listening to them intently.

"And that's when I smashed him in his robot face!" Raphael exclaimed proudly.

"Then I managed to deactivate the bomb," Donatello added. "The citizens are safe for now."

"And I looted their closet," Michelangelo said proudly, producing a rectangular item a few inches long with small pink buttons on its sides.

His brothers exchanged surprised glances.

"The Kraang have closets?" Leonardo whispered in disbelief.

"Give me that," Donatello ordered, snatching the item from his brother's grasp. "We don't want you to activate it by mistake."

"Hey!" Michelangelo protested.

Splinter smiled at the four turtles.

"I'm proud of you, my sons," he told them. "But remember, each battle is a new one and the outcome is never certain. You have to keep ready for the unexpected."

"Hai, Sensei," the four turtles chorused.

Splinter gestured that they were free to go, and Raphael turned to his brothers.

"But it's still a victory. I say we deserve that pizza movie night, oh yeah!"

His brothers gave him a high-five under Splinter's fond gaze.

Of course, it meant that he would have to use earplugs if he wanted to get some rest, but he was willing to humor his children. They had earned it. He listened to Michelangelo's suggestions for the movies, to Leonardo's input, to Raphael's statement that he wouldn't be the one making popcorn this time, to Donatello's 'Oops'…

 _Oops?_

There was a loud buzz, a puff of pink smoke, and the giant ninja rat disappeared from view.

His four sons turned to him.

" _Sensei!"_

When the smoke dissipated, they were left gaping at the scene.

Their father wasn't there anymore.

In his place stood a small mutant rat, standing on his two feet and floating in Splinter's large robes. A childish mutant version of the ninja master.

"Where am I?" The child asked in a high-pitched voice, and in Japanese.

He looked at the dojo and at the four bewildered turtles in front of him, then glanced at his furry arms in confusion.

"Who are you? Why are you wearing these costumes? And me?"

The rat frowned.

"Did you kidnap me?"

As he didn't receive an immediate answer, he ran to the closest turtle – who happened to be a rather shell-shocked Leonardo – and began pounding his shell.

"Give me back to my family this instant!"

Leonardo gently caught the rat's tiny fists in his three-fingered hands, his face keeping a blank expression.

Michelangelo recovered first from his shock.

"Donnie, did you happen to activate the Kraang device by mistake?" He said cheerfully, although it was a little strained.

Donatello closed the mouth he had left wide open during the last two minutes, startled out of his shocked state by the accusation.

"I…I…" He eloquently answered.

But Michelangelo didn't expect an answer. His focus was fully on the rat child.

"Aww, he's so cute!" He exclaimed, automatically switching to Japanese as he watched the small mutant curse in this language. "Don't you think he looks a lot like Raph?"

Raphael smacked his brother without even looking at him, the gesture an automatism. Splinter turned around to growl at Michelangelo, showing his tiny white teeth. His fists were still imprisoned in Leonardo's hands, and he undertook to free himself by biting the green skin.

"Ouch!" Leonardo shouted, releasing the mutant child.

Splinter ran to Michelangelo and kicked his legs.

"I am not _cute_! I am Hamato Yoshi, heir to the Hamato clan, and you will address me with proper respect! Now where is my family?"

The child looked from side to side, searching for something.

"Did you kidnap my brother Saki too? I swear, if you hurt him, you'll regret the day you were born!"

Raphael took a ragged inspiration, finally remembering how to breathe.

"Okay. No movie night."


	2. Say Hello to Your Daddy

_AN: Thanks for your feedback! I wonder how the boys will handle the situation._

* * *

 **Say Hello to Your Daddy**

* * *

Leonardo licked the bite marks on his hand as he watched the child version of his rat father kick Michelangelo. Considering the boy was still wearing Splinter's clothes, it was a miracle that he hadn't tripped over his robe.

"Hey! Don't do that, it hurts!" Michelangelo protested, trying to catch Splinter's shoulders to keep the child at arm's length.

"Please tell me it's a nightmare," Leonardo muttered. "Someone please pinches me."

"No problem," Raphael shrugged with a half-smile, extending his arm to comply. "Always happy to help."

Leonardo yelped.

"It was just a figure of speech, Raph!"

Raphael's innocent face could have rivaled Michelangelo's on his best days.

"This is messed up," Donatello stated, completely ignoring his brothers' antics. He was looking at the Kraang device in his hand as if it was haunted. "Let's hope it has a reverse functionality."

The tall turtle tried to push different buttons while Leonardo and Raphael took a careful step backwards, but nothing happened. Splinter finally tripped over his clothes and sat on the floor, still kicking Michelangelo.

"No, nooo! Good Splinter, no kicking!" The orange-clad turtle tried to reason with the child while he danced from one foot to another to avoid the little legs.

"My name is Yoshi, not Splinter!" The rat protested, not stopping his struggle. "And why are you talking to me as if I were a baby? Are you stupid?"

"Well, now that you're asking…" Raphael began, but Leonardo nudged him with a deadpan look.

"Not helping."

"I think it's out of juice," Donatello muttered. He took a deep breath. "Okay guys, I officially announce that I won't be able to fix that on the spot. We need to find a new power source for this, not to mention I have to figure out how it works."

"So you're basically saying that we're stuck with Tiny Splinter here?" Raphael said, disbelief in his voice.

"My name is YOSHI!" The rat shouted. "Now tell me where my family is!"

"Right here," Raphael muttered under his breath, crossing his arms.

Donatello tilted his head. He spoke at full speed and with great detachment.

"Okay. You're our mutant rat father turned into a mutant rat child with the mind and memories of his youth."

Splinter looked at him in incomprehension. Leonardo, Michelangelo and Raphael gaped at their brother.

"Donnie!" Leonardo finally exclaimed, in English so that the child wouldn't understand. "You can't tell him that!"

"And why not? I've read somewhere that you shouldn't lie to young children," Donatello protested.

"The circumstances are special, Donnie," Leonardo said between gritted teeth.

"You think you know better?" Donatello said, clearly offended. "Be my guest."

Splinter was looking at them both, still vaguely kicking and obviously curious to know why they were arguing. Leonardo took a deep breath and turned to him, kneeling to be at his level. Right now, he wanted to be anywhere but there. He tried to meet the child's gaze, but it was as if he was looking into his father's eyes and the feeling was too weird for him. He ended up focusing on a spot on the wall behind.

"Okay, uh… Yoshi. Please stop kicking my brother and listen to me. We're not your enemies and we didn't kidnap you, we're… uh…"

Leonardo racked his brain in search of a suitable answer.

"Your…gardians," he went on. "We're from the Hamato Clan too, see?" He produced a throwing star and showed the child the symbol embedded in it. Yoshi stroked the lines with a pensive expression. "I'm Leo. The orange one is Mikey, the purple one is Donnie, and the red…"

"…and hotheaded…" Michelangelo interjected.

"…and the red one is Raph," Leonardo finished. "We're brothers. Your parents asked us to keep you safe while they deal with…a situation…requiring discretion…that is…"

He sent a desperate look to his brothers, asking for help.

"Oh no," Raphael whispered to him in English. "I want to enjoy the very rare Leo-lying-to-Splinter's-face thing. You're on your own."

He smiled smugly as Leonardo glared at him. Donatello was still sulking and didn't bother to speak. Luckily for the poor leader, Michelangelo decided to help.

"You see, bad aliens have been mutating good people," he said gleefully. Maybe glee wasn't the most appropriate emotion for such a sentence, but he didn't want to scare the child. "That's why we're turtles, and you're a rat. We're taking care of you while the rest of your clan is busy kicking the aliens' a…"

"Language," Leonardo interjected just in time.

Yoshi's shoulders slumped and his lips quivered at the words.

"Aliens? Mutating?"

He looked at his hands as if he was seeing them for the first time.

"It's not a costume?" He said in a small voice.

"Uh, no, it's not," Donatello said softly. "Sorry. But…"

He exchanged looks with his brothers.

"We'll find a cure soon. And you'll be back to normal, how is that?"

Yoshi seemed to consider the offer for a while.

"Where is my brother Saki?" He finally asked.

"He's in a separate location," Leonardo answered, inwardly wincing. "But he's in great shape, don't worry."

"That's too bad, by the way," Raphael grumbled in English.

"I want to see him," Yoshi demanded. "Bring me to him, now."

Leonardo sighed. All he wanted now was to put an end to this terribly awkward conversation.

"It's not possible, I'm afraid," he said. _He kind of wants to kill you._ "But Mikey will show you the lair, okay? It's a great place to be. And it won't last long anyways, because Donnie – he's a genius – will find a solution."

Leonardo stood up while Michelangelo took his place, extending a hand to the child.

"Come with me, little dude. I'll show you our home, and maybe we can find you new clothes. Then we can play videogames, or read comics, or eat pizza. Do you like pizza?"

Michelangelo's voice sounded as if it was completely normal to suggest these activities to your ninja master of a father, and Leonardo admired him for that. Yoshi didn't take the turtle's hand, but he hesitantly nodded. Leonardo sighed in relief as he left the dojo behind Michelangelo.

* * *

"How long will it take?" Raphael asked, leaning over Donatello's shoulder as the genius began sketching at his lab's desk.

"I don't know, Raph," Donnie answered, irritated.

"Give us your best guess," Leonardo suggested, leaning over Donatello's other shoulder.

Donatello sighed.

"I don't know, Leo. Hours? Days, maybe?"

Leonardo moaned.

"We're stuck with Tiny Splinter for _days_?" Raphael exclaimed.

All of that right in Donatello's ears.

The purple-clad turtle took a deep breath and set down his pen. He grasped his brothers' bandana and gave them a sharp tug to move their heads away.

"And it will be more than that if you don't let me focus," he said reasonably. "So let me work IN PEACE and maybe I'll make PROGRESS!"

Leonardo and Raphael shared an awkward look. Donatello was obviously on edge – no kidding. They all were.

"Sorry, Donnie," Leonardo said sheepishly.

He headed for the door, followed by Raphael, when Michelangelo burst into the room.

"Hey, Dee! How is it going?"

"Well, as I was just telling the others, I need PEACE and QUIET," Donatello emphasized. Mostly calmly.

Michelangelo looked at him, then at his other brothers, before nodding slowly.

"Oooh. Oooh, I see. You need PEACE and QUIET, so you threw them out. I get it. Now, what are you doing? Can I take a look at it?"

Donatello rested his elbows on the desk and buried his face in his hands. Michelangelo took it as a yes and came closer to him.

Something suddenly occurred to Leonardo.

"Mikey, where is Splint… uh…Yoshi?"

"I left him in my room, he wanted to read my comics," Michelangelo announced proudly.

"You left him alone?" Leonardo asked as a feeling of dread slowly spread in his body.

"Of course I did! Why not?" Michelangelo protested.

"Oh, I don't know, Mikey," Raphael said wryly. "Maybe because he's a young child who doesn't really trust us? Did you truly believe that he was interested in your comics? I don't think he reads English!"

Michelangelo crossed his arms.

"The pictures are really cool, you know," he answered angrily. "And I did believe him! I trust people, remember? Even people who don't deserve it!"

"He has a point," Donatello interjected from his desk. "Remember Bradford?"

Leonardo didn't wait to hear the rest of the argument. He raced to Michelangelo's room, where Yoshi wasn't. He quickly searched the lair – no trace of the mutant rat.

Yoshi was gone.

 _Did we truly manage to lose him after not even an hour?_ Leonardo thought idly.

Then reality hit him. Their father, now a child, was wandering the sewers of a foreign city. Alone. As a mutant.

"GUYS!"


	3. Come Back Here!

_AN: Tiny Splinter is on the loose. Let's hope his sons find him soon._

 _Thanks for your reviews! I love them._

* * *

 **Come Back Here!**

* * *

 _Splash!_

The sound resonated through the sewer tunnel. The small mutant froze, every sense on alert. When nothing happened, he relaxed and slowly put his foot out of the water puddle.

At least he hoped it was water. The smell was strange in these tunnels, but it wasn't unpleasant for his nose. His _rat_ nose. Should he call it a muzzle?

Yoshi rubbed his arms. The water had splashed the lower part of his body and he was shivering. He should have been more careful, but he hadn't thought that the ground would be so uneven. The water puddle had been deeper than he had expected it. The T-shirt the giant orange turtle – _Mikey_ – had found for him didn't do much to help against the cold.

The child frowned at the thought of the turtle. He had a feeling that he and his blue brother weren't being entirely honest with him. Why would his parents leave him in the care of perfect strangers without giving him an explanation?

Or maybe they had told him something, and he didn't recall what it was. His memories were a blur; he didn't even know how he had arrived there, and it disturbed him.

On light feet, he continued to move forward. There had to be a source of light somewhere close, because the darkness wasn't complete.

 _What a creepy place,_ he thought, looking at the concrete walls of the round-shaped tunnel. He tried not to imagine what lurked in the shadows. Ghost stories were funny on winter evenings, when he was warm and safely tucked under a blanket with his brother Saki, not when he was wandering a dark tunnel alone.

He refused to allow fear to control him. He needed to be strong to find his way out of here and see for himself what was happening.

And more importantly, he had a brother to find.

* * *

"He can't be far," Leonardo said. His voice was strained.

Raphael huffed with irritation to conceal his anxiety. The four turtles had split up and searched the different tunnels close to their home, with no luck. How could a child have escaped them so easily? Even if that child was a ninja in training.

"Obviously he could, Leo," he retorted. "Or we would already have found him."

Leonardo didn't bother to answer, obviously lost in thought. Raphael didn't push it. He knew his brother felt responsible for the fact they had lost their father in the sewers. He probably thought he should have known that Michelangelo would leave Yoshi alone, and that the child would sneak out. And if Michelangelo's morose face was any indication, the orange-masked turtle felt guilty about it too – maybe even about bringing the Kraang device home. Although it had been Donatello who had caused their father's predicament, which meant that the genius was certainly blaming himself too.

Raphael sighed. Even if it felt good to be the one who had nothing to feel bad about for once, he didn't like seeing his brothers downcast.

"Hey," he said gruffly. "We'll find him. If anything, the fact we didn't already proves that he still has his stealth abilities."

"Highly unlikely," Donatello muttered. "Coordination in a child this young doesn't allow to…"

Raphael glared at him. If his genius of a brother didn't do his bit, it wasn't going to work.

"…buuut maybe Splinter's spirit – adult Splinter's spirit – is watching over his young self somehow," Donatello quickly added in a high-pitched voice.

Raphael smiled. Much better.

"So what do we do now, Leo?" Michelangelo asked, turning to the leader.

Leonardo tapped his chin pensively. He had never been more grateful for his ability to keep calm in crisis situations. It allowed him to ignore the little 'we-lost-him-where-is-he-we-lost-him-he's-gonna-drown-he's-gonna-be-found-he's-gonna-be-hurt-we-lost-him-how-could-we' panicked voice in his head.

"I don't understand. We should have seen him or his tracks. There are water puddles everywhere after the last rain. The only possibility is that he took another route, but we've checked every tunnel leaving from the lair."

The four turtles fell silent, until Donatello snapped his fingers.

"We've checked every tunnel we could walk in, yes. But Splinter is much smaller than us right now. He can go where we can't."

"So Splinter took a route that we didn't check?" Michelangelo asked.

"It has to be," Leonardo answered.

"A route that only somebody small could use?"

"That's the idea," Donatello said.

"But Splinter could have used it, because he's small right now."

"Yes, Mikey," Raphael replied, irritated. "That's what Donnie just told us."

"And it could be, let's say, a small hole in the wall caused by a recent crumbling?" Michelangelo went on, unfazed.

"It could," Donatello approved.

"Oh, okay."

Michelangelo fell silent. His three brothers looked at each other and shrugged. Then it clicked.

"Mikey, do you know where such a hole could be found?" Donatello exclaimed.

"Of course, bro," Michelangelo nodded. "It's right there."

He pointed at a spot behind his brothers, and the three turtles turned around to look at it. There was indeed a small hole in the sewer wall. Raphael crouched to examine it.

"Does it connect with another tunnel?" Leonardo asked, excited.

"Let me check," Donatello answered.

He took his T-Phone and looked the sewers' map up. He frowned.

"It does, with the maintenance tunnel. If Splinter took this route, the probability he'll meet a human just increased greatly."

"And I think he did," Raphael said gloomily, standing up. He was holding a few brown hair.

"Then we've no time to lose," Leonardo declared, his eyes narrowing. "Let's go."

* * *

Yoshi yawned. He was beginning to get tired. Was there nobody in these boring tunnels? And he was hungry, too. Maybe he should have tried this pizza Mikey had been talking about. He still could have snuck out later…

The small mutant turned around another corner and stopped.

There! A man in a yellow suit and carrying a torch! The man was looking at a kind of gauge and hadn't heard him arrive.

"Excuse me, Sir, where am I?"

The man started. He shouted something that Yoshi didn't understand and shook his torch wildly.

"Good Sir, I only want your help…"

The torch lighted Yoshi's figure and the man shrieked. He released the torch and ran away.

"No, please, wait!"

"He's there!" A voice said from behind.

Yoshi recognized the voice of the blue-masked turtle – _Leo_ – and ran for his life, following the man's trail. It wasn't hard, considering the sewer worker was still screaming at the top of his lungs.

Yoshi saw something fly in the air above him and hit the man, who suddenly stopped shouting and fell down. The turtles behind him were coming closer, but he couldn't allow them to catch up with him. He didn't want to be stuck with them while his brother was who knew where… If he had been able to find one human, there was bound to be more… This one hadn't seemed to understand him, which was annoying, but he had to keep trying…

He took in his surroundings, looking for an escape – maybe another hole in the wall, where the turtles wouldn't be able to follow him… There!

Yoshi crouched to reach the hole.

"Oh no you don't!" Mikey said.

The small mutant felt something coil around his arms and torso, almost gently, and he realized that he couldn't move.

Tears came to his eyes as he realized that his escape attempt had failed.

* * *

"LET ME GO!" Yoshi was shouting.

He was no longer restrained by the chain of Michelangelo's kusarigama, but Raphael's grasp on him was unescapable. His head was level with Raphael's plastron – a precaution the turtle had taken after Yoshi had bitten his shoulder.

"Can I knock him out too?" Raphael grumbled.

"No, you can't," Leo retorted.

"Gag him, then."

"Sure, and once we bring Splinter back, good luck explaining that to him."

Raphael gulped.

"Okay. No gagging."

Leonardo smiled. He felt so much better now that they had found Yoshi.

"Start going back to the lair. We'll catch up with you in a few minutes."

Raphael nodded and moved away, still carrying a very mad and very cursing mutant rat. He felt extremely uneasy at the thought it was his own father who was insulting him right now. He didn't understand half of the Japanese words, but he got the general idea.

 _I had no idea that Splinter knew so many swear words, even less as a child. It must be Saki's influence on him._

Leonardo watched his brother depart and huffed. He was carrying the sewer worker with Michelangelo's and Donatello's help to one of the maintenance rooms. It would have been dangerous to leave him unconscious in a sewer tunnel. Raphael's blow had been precise and efficient; the hilt of his sai had hit the man's temple with the exact strength required to knock him out for a few minutes.

"I'm so sorry about this," Leonardo whispered to the unconscious worker. "Please accept my most sincere apologies."

"He can't hear you, Leo," Michelangelo remarked.

"I know, but I'm still feeling better."

Once in the room, they sat the man against the wall and hid behind the door. When he began to stir and the turtles were certain that he would be alright, Leonardo motioned for his brothers to leave.

They found Raphael a few tunnels ahead. Yoshi was now silent, his lip turned up in a pouting expression. When he saw the other turtles, he glared at all of them.

"How are you feeling?" Michelangelo tried shyly. He felt bad for having used his chain to catch the child.

Yoshi turned his head and didn't answer.

"We're your friends," Leonardo tried in his turn. "We only want to help you. Humans… Most of them don't understand mutants."

He thought for a while.

"Even if a lot of them got mutated in the alien attack we told you about. The one that compelled your parents to make the decision to leave you with us… And, uh… they would be really sad to know that you ran away like that. Because we're in touch with them, you see, and… uh…"

Donatello nudged him with a warning look, too late.

"You're in contact with my parents?"

Yoshi perked up.

"Can I talk to them?"

Leonardo inwardly winced. He hadn't thought this through.

How he hated lying.

"Uh, no… Not right now. They're busy. Sorry."

"Oh," Yoshi said, his shoulders sagging.

"You know," Donatello said softly, "it would be a lot easier if you just let us help. It's the most sensible thing to do. And you're a sensible boy, right?"

Yoshi considered this for a while, his eyes narrowed.

"Okay," he finally said.

The rat didn't miss the turtles' expressions of utter relief.

"I'm sorry I ran away," he added with a sheepish expression, and he saw them melt. He smiled inwardly and shifted in Raphael's arms. The red-masked turtle allowed him to move so that he was more comfortably settled. Yoshi yawned. He was feeling so tired, and he was warmer now… Maybe it wouldn't hurt to close his eyes for a short while…

A few minutes later, he was sound asleep. Raphael held him a bit tighter, his expression soft.

"He's so cute," Michelangelo whispered next to him. "Can I carry him?"

Raphael narrowed his eyes and turned to move Yoshi away from his brother.

"No."

"Oh come on, Raph! Pretty please?"

"No way. I carried him while he was biting and kicking and shouting insults, I'm not giving him back to you now that he's calmed down."

"But Raaaaaph!"

"Hush, you'll wake him up."

Leonardo watched them with a grin. He had a vague feeling that Yoshi's reversal was a bit too sudden, but he dismissed it. That reasonable attitude was more like the Splinter he knew. Yoshi had just been understandably upset by the situation. Now he would cooperate, and soon Donatello would find a way to bring back the adult version of their beloved father.

In the meantime, he had to admit that the vision of Tiny Splinter huddled in Raphael's arms was very cute indeed.


	4. Ratsitting

_AN: Where the turtles get used to having Tiny Splinter in the lair. Longer chapter, I've hesitated to split it and I finally decided against it. What do you think?_

* * *

 **Ratsitting**

* * *

In his lab, Donatello was trying to focus on fixing his last mistake. He had thought that his Kraang technology knowledge – laboriously accumulated through hours of trial and error – would be enough to allow him to play safely with the new device Michelangelo had found.

He had been wrong.

As a consequence, his father was now one-third of his normal height and he was convinced that he lived in Japan with his parents and his dear brother Saki. Granted, since Yoshi had woken up, he was very cooperating. He was polite, didn't try to run away and hadn't mentioned once Saki or the events of the day before.

But it only partially released Donatello's guilt. Worst-case scenarios played over and over in his very imaginative brain. What if the Kraang device was broken beyond repair? What if the transformation was irreversible? Had they already lost their father, the reasonable, levelheaded, supportive father they all desperately needed?

The purple-clad turtle breathed deeply and used a meditation technique Splinter had taught him to focus his thoughts on the matter at hand. He wouldn't be of any use to anyone if he kept feeling sorry for himself instead of working on a solution.

He had to fix this mess.

He _would_ fix this mess.

With determined gestures, he took the incriminated Kraang device and tried again to make it work. He grabbed a tiny screwdriver and used it as a lever to open the device, and…

"What are you doing?"

The purple-masked turtle started at the unexpected interruption and nearly pushed the screwdriver in his eye. He placed his hand against his plastron, panting, and turned around to look at the small mutant rat who had just come out from nowhere. Weren't Raphael and Michelangelo supposed to take care of the child while he worked on finding a solution to their predicament? Leonardo had disappeared in the dojo right after breakfast, on the pretext of meditating. Obviously, he was having a hard time coming to terms with the whole Tiny Splinter disaster.

"Howdoyou… How do you keep doing that?"

Yoshi smiled, very pleased with himself.

"Stealth is part of being a ninja. Maybe you'll understand that one day."

Donatello shook his head, not knowing if he should feel irritated by the boy's smug reply or moved to discover that this annoying ability of his father – to move like a ghost and appear suddenly at the most embarrassing moments - was a childhood's thing. He chose to focus back on the device in his hand.

"What is that?" Yoshi asked.

"It's an alien device," Donatello replied.

"From the same aliens that mutated us?"

"Yes," the turtle answered without hesitation. After all, it was the truth, and it was also compatible with the story Michelangelo had come up with.

"What does it do?"

"It…" _mutates fathers into young children…_ "I'm not sure. I'm trying to understand how it works. I think it's out of power…"

"What will you do then?"

"I'll… try to replace its energy source."

"Like a battery?"

"…Yes. Like a battery."

"And what is that?"

Standing on tip-toe, Yoshi pointed at the Kraang communication orb.

"It's an alien device."

"From the same aliens that mutated us?"

Donatello bit his lip. Yoshi was full of questions, and it didn't bother him to repeat himself.

Well, he had come to the right turtle for the job.

The genius stood up and offered to lift the boy so he could have a better look at the treasures on the shelves. Maybe a break would be useful, and Donatello wasn't going to miss the opportunity to display his wide knowledge.

"Yes. You see, it works that way…"

From the corner of his eye, he saw Raphael and Michelangelo high-five in the doorway of his lab.

"I told you Donnie wouldn't mind the questions," Raphael whispered.

Donatello stifled a snort. So his brothers had conspired against him, uh?

He glanced at the enthusiastic miniature version of his father in his arms and decided that he didn't mind.

* * *

An hour later, Donatello felt refreshed. He had showed his entire lab to Yoshi. The child had showed more interest than Splinter did these days. Donatello fondly remembered a time when his father always asked what he was up to. Maybe he had wanted to make sure his son wasn't going to involve in too dangerous activities. The genius had to admit that his record was pretty bad as far as safety was concerned.

In any case, it had felt nice. Maybe watching over Yoshi until they could transform him back to his adult self wouldn't be too much of a chore after all.

"And now, let's have lunch," Donatello said cheerfully.

"What are we going to eat?"

"Well…"

From the living room, Michelangelo shouted.

"Pizza's ready! Hurry up or you won't have any!"

"…Pizza, I guess. Come, we shouldn't ignore that threat. Mikey never jokes around with food."

"You ordered pizza again?" Yoshi asked, his tiny hands on his tiny hips. "I thought it wasn't healthy. What about vegetables for a change? My mom says they are good for your health."

Donatello looked at him sheepishly.

"For humans, maybe," he coughed. "Mutant turtles must have a different diet."

At least, none of them had ever been sick because of an overconsumption of the delicious food and its greasy toppings.

"But I'm not a turtle. I'm a rat."

Yoshi didn't sound particularly sad at the fact. He had accepted it like only young minds could.

"… There will be cheese."

The child perked up.

"What are we waiting for?"

Donatello smiled and led the way to the living room couch where they would take their meal. Probably not the best place to eat with a child, but they weren't raising him - the mere idea felt ridiculous. They were simply babysit… _rat_ sitting him for a while.

Yes, the couch would do.

* * *

After lunch, Donatello went back working in his lab and Leonardo – who had been rather quiet during their meal – had disappeared again in the dojo. Michelangelo suggested playing video games to Raphael and Yoshi, and they both accepted. They began a racing game that Yoshi kept losing, no matter how much Michelangelo tried to help him by clearing the road or attacking Raphael's car.

"You have to focus," Raphael said gleefully. "Or else you won't accomplish anything."

In a corner of his mind, he hoped that Splinter wouldn't remember that conversation when he would be back to his old – and older - self. Raphael had no doubt that it was only a matter of time before it happened. Donatello would find a solution. The genius had seemed quite relaxed at lunch, and said that his conversation with Yoshi had given him ideas.

In the meantime, Raphael enjoyed the opportunity to say these words to his father.

"Uh-huh," Yoshi whispered. Something was obviously troubling him.

Raphael put his joystick down.

"What's on your mind?"

"Why were you sad?" The boy asked out of the blue.

Raphael blinked. Had he looked sad to the young mutant's eyes? He had looked angry, sure, and teasing, probably, and strong, of course… But sad? When?

"Uh?" He answered with great eloquence, prompting the boy to go on.

"At lunch. When you found this leaf on your pizza. You were sad."

All of a sudden, Raphael's expression shut down. He hadn't been aware of that, but Spike's transformation into Slash was very recent and he still caught himself longing for him whenever something triggered a memory. Splinter had helped him with the grief, but…

"Why were you sad?" Yoshi repeated because the turtle wasn't answering fast enough to his taste.

"Yoshi…" Michelangelo whispered.

"Why?"

The boy was stubborn, wasn't he? Something else Splinter still was. Raphael played with his wrists' wrappings.

Michelangelo clasped his hands.

"And I think we can play a fighting game now! Yes! Great idea, me!"

"Why?" Yoshi repeated.

Michelangelo fell silent.

Raphael fidgeted. The boy didn't quit, did he? And the turtle was finding hard to ignore his question and dismiss him. Why?

 _Because deep down, he's still your father._

"Fine," the red-masked turtle snapped. "I _was_ sad because that leaf reminded me of my pet, and he's gone. Happy now?"

Yoshi tilted his head.

"I had a hedgehog once. But he was flattened by a car. Was your pet flattened by a car too?"

Raphael gaped. It was asked with such candidness that there was no doubt the child meant no harm.

"Uh… No, it was… another kind of accident," he finally stammered. "And Spike isn't dead. He's just not the same anymore, and it makes me sad."

Yoshi nodded gravely.

"And…"

"What again?" Raphael exclaimed, exasperated.

"Why did Leo and Donnie refuse to play with us?"

The two turtles exchanged an uneasy glance. They couldn't exactly tell Yoshi that Donnie was trying to fix him, or that his presence was weirding out Leo so much that he was trying to avoid him, whether or not it was conscious. The child wouldn't have understood.

"Uh… Donnie's busy working, and Leo's busy meditating," Michelangelo answered. "Boring grown-up things that I personally don't understand."

"My parents always say that brothers should enjoy each other's company."

The young rat's voice was sad. There was no doubt he was thinking about his own brother, Saki. The one who was going to betray him and destroy his first family. Michelangelo shook his head as if it could dispel the ominous thoughts. It was time for a change of mood.

He smiled mischievously.

"You know what? I've got a great idea. Go fetch Donnie, Yoshi, and don't take no for an answer. We're going to have fun!"

The child nodded, intrigued, and left them. Raphael tilted his head.

"And what about Leo?"

Michelangelo grinned.

"Oh, believe me, he'll come. He'll come."

* * *

Leonardo was trying to empty his mind, with little success. He kept remembering the overwhelming panic he had experienced when he had understood that Yoshi was missing. He was regularly checking on him, making sure that his brothers were true to their word and at least one of them was watching the boy at all times, but he had been careful not to make his presence known.

He wasn't very proud to be using meditation as an avoidance strategy, but seeing his father like this was too weird. Besides, he didn't know how to behave with children. After all, it had taken a toddler girl twenty seconds to convince him to have a tea party in her bedroom while his brothers were getting their shell kicked by Raphael's former pet.

Although Leonardo couldn't have known it at the time, so maybe it wasn't on him.

The blue-masked turtle sighed. Maybe it was time to face his awkwardness and engage in some activity with Yoshi. It wasn't fair to let his brothers do all the ratsitting, and…

 _Boom. Crash._

Leonardo was immediately on his feet and running out of the dojo, wondering what had happened. Had Yoshi run away again?

"Oh yeah! That's the spirit, dude!"

The blue-masked turtle gaped. Michelangelo was on his skateboard, sliding on everything in the living room and beyond.

"Mikey! What are you doing?"

"Skateboarding, Leo! Isn't it obvious, bro?"

"Splinter said not in the lair!"

"But look, he's enjoying it!"

Raphael brushed past his brother on his own skateboard. Yoshi was on his shoulders, enjoying the air blast. His whiskers were all disheveled.

"Raph! You're helping Mikey with this scheme?"

"Relax, Leo. We need the fun."

A flying skateboard propelled by something that looked suspiciously like a rocket almost knocked Leonardo out. The turtle on it shouted his apologies.

"You too, Donnie?" Leonardo exclaimed.

"Eheheh… eheheheh…"

Leonardo threw up his arms. The lair was pretty much already trashed anyways. And he _had_ wanted to engage in an activity with his family, hadn't he?

This was the perfect occasion.

With a grin, Leonardo ran to his room to retrieve his own skateboard.

* * *

The turtles and their now childish father were having lots of fun. Donatello had somehow built a racing circuit inside the living room, and they were making good use of every ground, wall or ceiling surface.

Their skateboarding session abruptly came to an end when a red-haired girl jumped the entrance turnstiles, obviously in a rush.

"Hi guys!" She shouted. "I'll chat with you later, I'm almost late and I don't want to make Splinter wait, he… Wait, I thought you weren't allowed to skateboard inside the lair? And who is this little one?"

April's brutal apparition had startled the boys. Michelangelo crashed against Raphael, who threw Yoshi to Donatello so he wouldn't be hit. Leonardo came to a stop next to the teenage girl, his expression sheepish. They had forgotten their friend's ninjitsu lesson with Splinter. In fact, they had altogether forgotten to warn her about the recent events.

Everything had happened so fast.

"Uh… about that…"

"Hi, beautiful lady," Yoshi greeted her, blushing.

April's eyes widened. In which language was he talking? She turned to Leonardo, who kept quiet. His fingers were fidgeting like they did when he was extremely embarrassed. It worried April, who looked at Donatello. The turtle put Yoshi down and lost himself in the contemplation of his feet.

"Donnie?" April said warningly.

"There was… an incident…" Donatello croaked.

He didn't finish his sentence.

Now April's worry was turning into full-blown anxiety. She looked at Michelangelo and Raphael, hoping that one of them would tell her what the matter was. _It can't be too serious_ , she tried to convince herself, _they were playing._

"Sensei is a child right now," Michelangelo announced proudly. "Look at him!"

April opened her mouth to talk, but no sound came out. Had she heard correctly?

Raphael whispered something to the little rat mutant, who nodded and bowed to her. April managed a poor smile and waved her hand. Now that she thought about it, he did look like a miniature version of Splinter. And… She briefly closed her eyes. Yes. He had his aura.

Her gaze darkened.

"What did you do this time?" She demanded of her boys.

* * *

"And he's only talking Japanese," April sighed. "Seriously, guys, you've got to stop putting yourselves in such situations."

"It wasn't planned," Donatello protested.

Everyone had gathered in the dojo, mainly because the rest of the lair was a mess. Yoshi was sitting under the tree with his arms around his knees, unaware that it was his usual place. He was watching the others discuss and felt excluded from the English conversation.

"I know it's disturbing," Leonardo sighed. "But you get used to it."

"Sure, Leo," Raphael snorted. "You kept avoiding the boy all day."

"What? I didn't!"

His three brothers lifted an eye ridge at this display of bad faith, their synchronization perfect.

"O-okay," Leonardo stammered, "Maybe I'm not entirely comfortable with him."

He felt bad talking about Yoshi as if he wasn't there.

April shook her head.

"Well, do you need my help? If not, I should probably head home. My lesson has been cancelled, and you four have some major cleaning up to do."

"No, April, you shouldn't," Leonardo protested. "You have to train regularly. And now that I think of it, we should train, too."

His brothers groaned.

"Oh come on, guys, we won't have training sessions outside for… hopefully not very long. We should at least practice in the dojo!"

Michelangelo sighed.

"You know, I really thought we would manage to skip training for an entire day. We were that close, guys! That close!"

Leonardo glared at him. His brother pretended to sulk, but stand up with the others and began stretching.

"Alright," Leonardo said after a while. Yoshi's attentive watch made him nervous. "Let's go through a basic kata first, okay?"

He began the first moves to show the others which kata he had in mind. Yoshi coughed.

"What?" Leonardo asked him in Japanese, curious and a little worried.

"You're doing it all wrong."

The blue-masked turtle opened wide eyes.

"Excuse me?"

"You're doing it all wrong," Yoshi repeated with great certainty. "You're supposed to balance your arms like this, you see?"

The tiny rat moved his arms to prove his point.

"May-maybe it's another version," Leonardo stammered, nonplussed. Was Tiny Splinter really criticizing a kata that Adult Splinter had taught him? This was mind-blowing.

Yoshi shook his head.

"It's not traditional. Who was your Sensei, I wonder?"

"I…I…"

"Look, I think it'll be better if I show you how it's done."

Yoshi stood up and placed himself in front of them with a serious expression. He was barely reaching Leonardo's waist. Raphael and Michelangelo chuckled while Donatello tried to hide his grin. Baffled, Leonardo automatically mimicked his stance.

"You begin like this… No, your hand has to be more open, you see?"

"I only have three fingers!"

"It's not an excuse."

Behind him, Leonardo's brothers were in stitches. Even April, who didn't understand a word, found it hard to keep her composure.

Leonardo bowed his head. This was going to be a looong training session.


	5. What Now?

_AN: Thanks for your reviews! And I do believe that Leo is good with children. But seeing his worshipped father as a child is a disconcerting experience for him._

* * *

 **What Now?**

* * *

"And why do I have to stay home and take care of the children? Do I look like a housewife to you?" Raphael shouted.

The red-masked turtle was fuming. Next to him, Michelangelo had his arms crossed and didn't look happy at all.

"There is only one child," Donatello interjected. He was standing beside Leonardo. "Except if you count Mikey, but I would say he's childish, not a child. And there is nothing wrong with being a housewife, not that you're one or should be one, of course, and…"

Raphael clenched his fists and glared at his purple-masked brother. Donatello made a prompt retreat, leaving Leonardo to deal with the furious turtle.

"Of course not, Raph," Leo said, his voice calm. "But Donnie says that we need to take another trip to TCRI because he needs a…uh…"

Donatello whispered something in his brother's ear. Leonardo looked puzzled, and his brother sighed.

"An alien battery," he said a tad louder, resigned to the fact that the exact name of the item he was looking for was beyond Leonardo's understanding abilities.

"An alien battery," Leonardo went on, unfazed. "And he can't go alone, and we can't take Splint… Yoshi with us, so we have to split up."

"I get that," Raphael retorted. "But why are you the one going with Donnie?"

"Because I'm less likely to turn this stealth mission into a full blown battle should anything happen?" Leonardo answered, tilting his head as if daring his brother to contradict him.

Raphael tried to think of a witty reply, but he found none. Which didn't exactly help to soothe him.

"And why is Donnie the one to go with you?" Michelangelo demanded in his turn. "I could go instead of him!"

Donatello looked at him with a perplexed expression.

"And do you know how an alien battery look like, Mikey?" He said in a long-suffering tone.

"No. But do _you_ know?" Michelangelo replied, facing his genius brother as if he was certain of his logical thinking.

Donatello tapped his chin, suddenly thoughtful.

"Well, not exactly…"

"You see?" Michelangelo triumphed.

"…but at least I've a vague idea. And I can hack the security system, which you absolutely can't."

"We could just break in," Raphael grumbled. "Who cares about a stupid security system?"

Leonardo put his hands on his hips.

"Stealth. Mission," he breathed.

Raphael and Michelangelo were about to protest again when a small and sleepy voice interjected.

"Where are you going?"

Leonardo bit his lip, trying not to let his exasperation show. Now they had woken Yoshi from his nap.

The leader knelt to be at his father's level.

"Donnie and I have an errand to run. Raph and Mikey will stay with you. I'm sure they'll be happy to play with you. You'd like that, right?"

The child nodded hesitantly and Raphael sighed while glaring at Leonardo. Now he couldn't keep complaining without letting Yoshi believe that he didn't want to stay with him, and he didn't want to hurt the child's feelings. It was a low blow.

Michelangelo must have had similar thoughts, because he softened and smiled at Yoshi.

"Don't worry, we'll take good care of you."

Leonardo saw an opportunity to leave without further drama and took it.

"See you later, guys! We should be back in two hours, tops."

* * *

Yoshi watched Raphael hit his punching ball from the kitchen, a piece of cheese pizza in his hand. They had played videogames again, after what the child had said that he was hungry. Michelangelo had approved and led him to the kitchen, while Raphael vented his frustration on the poor item.

The mutant rat was thoughtful. With only two turtles in the lair, maybe it was time to move on to Phase Two of his Plan. Especially as the blue one – the leader of the group - wasn't there.

Phase One had been less of a chore than he had believed. Playing Obedient Yoshi had allowed him to enjoy the turtles' company while watching them in search of weaknesses – something he was being taught to do.

But he hadn't forgotten about his quest.

The tiny mutant turned to Michelangelo and took his sweetest voice.

"Mikey, may I ask you a question?"

Michelangelo stopped chewing his pizza and opened his mouth to answer.

A nasty sight.

"Of course! What do you want to know?"

"Is 'brainless moron' a compliment?"

Michelangelo's face dropped.

"No… No, it's not. Why?"

"Because Raph was saying that you were a 'brainless moron' yesterday."

"He was, uh?"

Michelangelo took an enraged mouthful of pizza. So Raphael had been calling him names behind his back? And in front of Yoshi of all mutants?

"Yes. He said you were the worst knucklehead he had ever met, and that…"

"Thanks, Yoshi. I got the message."

Michelangelo proceeded to eat every last piece of pizza to hide his hurt. Yoshi felt a pang of guilt. He had made up the insults, selecting them with an instinct that he didn't fully comprehend.

Obviously, they had hit home.

"Hum, I need to use the bathroom," Yoshi said.

Michelangelo didn't answer.

* * *

Leonardo stood guard while Donatello searched the room for the battery he needed.

Coming inside had been a piece of cake. The purple-masked turtle had deactivated the new security system, Leonardo had knocked out a guard or two, and both had slipped inside the building.

For the leader in blue, it was a relaxing mission. He wasn't afraid that Raphael would discuss his orders or charge ahead, or that Michelangelo would get curious and trigger an alarm. And as April wasn't involved in any way, Leonardo was confident that Donatello wasn't going to lose his head at the worst possible time.

Not that Leonardo minded having his three brothers with him. They were all valuable ninja and complemented each other well. It was just that once in a while, it felt good to see a plan unfold like it was supposed to.

His only concern was for Yoshi. Of course, Raphael and Michelangelo wouldn't let anything happen to him, but Leonardo couldn't help worrying.

"I hope everything is fine at the lair," he whispered.

"Of course it is, Leo," Donatello soothed him. "You worry too much."

* * *

"Raph?"

"Yes, Yoshi?"

"What's a 'bloated buffalo'?

Raphael stopped hitting his punching-ball in shock.

"Where did you hear that?"

"It's Mikey. He said you were the most impressive of 'bloated buffalos'.

"He did?"

Raphael's tone was low and threatening.

"Yes. Just after calling you a 'mean green machine'."

Raphael clenched his fists. Yoshi yawned.

"I think I'll take another nap," he said innocently.

"Yes. Yes, good idea," Raphael muttered absent-mindedly.

* * *

Not ten minutes later, Yoshi was leaving the lair on light feet. Furious but muffled shouts could be heard from the kitchen. Raphael and Michelangelo were obviously trying not to disturb him, and the mutant rat felt another pang of guilt. The turtles had been very nice to him. They didn't deserve to be tricked like that.

 _But they don't want to tell me where my brother is,_ he reasoned. _And I need to know._

* * *

"Leo, I've found it!" Donatello whispered. "We can go!"

Leonardo looked relieved.

"Perfect. I'll call the others to tell them."

Donatello rolled his eyes in mocked exasperation.

"Leo, we'll be back at the lair in no time at all. Stop worrying."

Leonardo averted his eyes and took his T-Phone.

"Just a quick call, that's all. So they don't feel too sidelined."

Donatello smiled knowingly.

* * *

"You always say I'm stupid!"

"And you always say I'm mean!"

Raphael had wanted to punch his brother and force him to apologize since the beginning of their quarrel, but something in Michelangelo's behavior made him hesitant. His brother wasn't usually this upset.

But then, so was he.

"You're mean when you're angry!" Michelangelo went on. His feelings were hurt, more because Raphael had been calling him names behind his back – and to their father – than because of the names in question.

"And you're stupid when you're… when you're stupid!"

"That's not a reason to tell Yoshi I'm a 'brainless moron'!"

"That's… what? I never did that! But you called me a 'bloated buffalo' in front of him!"

"No way!"

The two brothers stopped talking and looked at each other, slowly realizing that they had been fooled.

"Do you think he would…"

"The little brat!"

The two turtles hurried to the room where Yoshi was taking his nap, determined to confront him.

To their dismay, the room was empty.

"He tricked us," Raphael muttered. "He never intended to cooperate after all."

The red-masked turtle took a deep cleansing breathe, trying not to let his disappointment crush him.

"Let's check the sewers like last time. He can't be far."

Michelangelo nodded and ran out of the lair after his brother. The search had barely begun when his T-Phone rang. He took it mechanically.

"It's Leo," he whispered, looking at the device as if it was going to bite him.

"What are you waiting for? Answer," Raphael said, secretly relieved that Leonardo hadn't called _him_.

Michelangelo tossed the phone to Raphael.

"No, you answer. I'm too stupid for that."

Raphael tossed the phone back to his brother.

"You do it, or this mean bloated buffalo is going to punch you."

Michelangelo gulped and opened his phone.

"Hi, Leo?"

He listened to Leonardo's reply.

"Already? Good, that's good. What? How is it going home?"

Michelangelo gave Raphael a panicked glance.

"Play it cool," Raphael whispered. "Tell him we have the situation well in hand. We'll probably find Yoshi at the same place he was last time. No need to worry Leo before we're sure there is something to worry about."

"We have the situation well in hand," Michelangelo repeated. "There is nothing to worry about. Nothing at all. We're safely home…"

They reached the tunnel where Yoshi had met the sewer worker last time. It was empty. Raphael's face fell. Michelangelo grasped the T-Phone with a bit more panic.

"That echo? Oh, nothing, we're playing videogames and… no, I'm not hiding anything from you! It's not like we lost Yoshi again or anything!"

Raphael grimaced.

* * *

On a random rooftop of the beautiful city of New York, a blue-masked teenage mutant ninja turtle let out a very unstealthy " _WHAT_ HAVE YOU DONE?"

* * *

Yoshi was disoriented. What was this place? It didn't look like anything he knew of.

The tiny mutant had managed to get out of the sewers by following a man like the one who had been afraid of him – this time, the mutant rat had stayed hidden – with the intent of reaching one of the secret places only Saki and he knew of. Maybe his brother had left him a message.

But now, as he looked at this entirely new city, Yoshi had a dreading feeling that he was further from his home than he had anticipated.

This wasn't Japan.

He began panicking. Maybe he should have stayed with the turtles a bit longer, tried to learn more. Maybe it wasn't too late? Had they even registered his absence?

A flash of steel in front of him. A feminine voice.

"Now look at that. A rat mutant."

Yoshi looked at the newcomer. He hadn't understood her, but she wore armor and looked like… a ninja. A kunoichi, to be precise. And there was something else he liked about the girl. She felt like… family.

Yoshi perked up. Surely she would help if she could.

"I'm looking for my brother Saki," he asked in Japanese. "Have you seen him?"

The kunoichi's eyes widened.

"Your brother Saki?" She answered, also in Japanese. Yoshi felt elated. She understood him! She wasn't afraid of him! "And who are you, if I may ask?"

"My name is Hamato Yoshi," the young mutant said proudly. "Can you help me?"

He missed the cold glint in her eyes.

"Of course I can. In fact, I know exactly where your…brother is. Do you want me to show you?"

Yoshi nodded enthusiastically and took the hand she offered.

"My name is Karai," the kunoichi said. "You're lucky I found you. These streets are dangerous at night."


	6. Brother!

_AN: Yoshi is in less than reliable hands… I hope it ends well._

* * *

 **Brother!**

* * *

"Let's go over it again," Leonardo said, his voice only slightly higher-pitched than usual. "He's not in the lair. He's not in the sewers near the lair. He's not on the surface of the sewers near the lair…"

The four turtles were standing on a rooftop that offered a clear view of the streets nearby. Their eyes were searching the shadows, trying to spot a tiny rat mutant.

"You know," Donatello couldn't help remarking to Raphael and Michelangelo, "the fact that he turned you against each other is pretty impressive. He must have planned it all along."

Raphael let out a tired sigh. He was more upset than angry right now.

"He's a lot to handle," he muttered. "We left him on his own for what, five minutes?"

"More like fifteen," a rather downcast Michelangelo whispered.

Raphael turned to him, surprised.

"What? I had the microwave clock in sight."

"There are so many useful ways to spend fifteen minutes of your life," Donatello mused. "Exchanging insults while looking at a microwave clock isn't one of them."

"You want to philosophize now, Donnie?" Raphael said, exasperated. "We know we messed up! No need to rub it in!"

"Yoshi doesn't have the strength to lift a manhole cover," Leonardo interjected, willing to redirect the conversation before any frustrated turtles could unwind in a violent way. "If he left the sewers, he must have followed someone."

Donatello tapped his chin.

"No repairs were scheduled in the sewers tonight, but I'll check out, just in case."

Before the tall turtle had the time to do it, though, Leonardo's T-Phone beeped. The leader took a glance at it and grew pale.

"What is it, Leo?" Michelangelo exclaimed, jumping to look over his brother's shoulder. "Oh no!"

"What?" Donatello and Raphael shouted.

Leonardo turned the screen to them.

"Now we know where Yoshi is," he said, his voice devoid of any emotion.

His brothers froze at the picture he had just been sent.

The picture of Yoshi happily waving at them with one hand, while the other clutched Karai's.

* * *

"Where are we going, Karai?" Yoshi asked. "It's taking a long time!"

"Don't worry, Yoshi," Karai answered, her voice unctuous. "We're almost there. The Shred… Saki will be so glad to see you again!"

"I can't wait to be with him!" The rat child said, beaming. "The turtles were nice, but they're not my family."

Karai kept her voice neutral.

"These turtles, they live underground, right?"

Yoshi nodded vigorously.

"Do you know where exactly?"

The child thought for a while and rubbed his head with his free hand.

"Uh… I don't remember," he finally said, sheepish. "I'm sorry, Karai."

"It doesn't matter," the kunoichi answered, hiding her disappointment. She would have made good use of the knowledge of where Leonardo and his family lived, but the rat was more important. She had been talking to him, and she was convinced that he was, indeed, Splinter. Or at least a childish version of Splinter. The memories he had from Japan and a young Oroku Saki couldn't be faked.

Her father was going to be pleased. Tonight, he would finally get his revenge.

She had also ensured that the turtles knew Splinter was with her. She wasn't sure if she had wanted to show off or if it was her way to get revenge on Leonardo for betraying her trust in the first place.

 _Let him fear for his father's life. Let him try and fail to rescue him._

There was no doubt that the turtles would try to rescue their father. But they were no match for the Shredder's wrath.

The kunoichi and the rat had arrived within sight of the Foot headquarters. Karai stopped and pointed at the building for her young companion's sake.

"Look, we're there."

Yoshi couldn't help shivering. The building looked threatening. Creepy, even.

"Saki is inside?" He said in a small voice. "It doesn't look very… welcoming."

"I know, I know." Karai smiled. "But I assure you, we'll give you a warm welcome."

Yoshi nodded courageously and tightened his grip on Karai's hand.

* * *

"Karai ratnapped him?" Raphael shouted, taking his sai in hand as if it offered him some comfort. "I'm going to kill her!"

"Dudes, that's not good," Michelangelo said anxiously. "We're not exactly in good terms with her right now, are we?"

"No, we're not," Donatello stated. "She'll bring him to the Shredder, that's for sure."

Leonardo's features were frozen in a neutral mask when he talked.

"Let's go, guys. We have a father to bring back."

Nodding, the three others followed him when he jumped on another rooftop, taking the route to the Foot headquarters.

* * *

"Amazing," the Shredder whispered. "Do we know what happened?"

Karai straightened up from her bow and shook her head. Next to her, Yoshi did his best to look unafraid.

He wasn't very successful. In his defense, the tall, armored man who looked at him with cold eyes tended to scare people.

"No. It looks like an experiment turned wrong, but I don't know for sure."

The Shredder shrugged.

"It doesn't matter. Well done, my daughter. Tonight, we shall have our revenge!"

Yoshi fidgeted. Building up his courage, he dared to talk. His voice shook slightly, but the words were recognizable. He was proud of himself.

"Uh, Sir? Where is my brother Saki?"

The Shredder laughed. It wasn't a pleasant sound, and Yoshi shrunk. At the moment, he regretted not having a shell like the four turtles who had welcomed him in their home. He was beginning to worry that he might have made a mistake in following the nice lady.

"Your _brother_? Your brother is no more, child. He was a lie. A fake. I destroyed him, like I'll destroy you!"

Yoshi froze. His brother? Destroyed? Cold, hopeless fear filled his heart.

"Wh-what?"

He turned to Karai.

"You said you were going to help me! I trusted you!"

Karai ignored the betrayal in the child's voice.

"I know. That's messed up, right?"

Shredder gave his daughter a proud smile and grabbed Yoshi by his collar. The child wiggled his legs, trying to get free, but the Shredder's grasp was unescapable.

"Too bad he won't even know why he has to die," he mused.

He turned abruptly towards the high windows of his throne room.

"Unless you want to turn him back into his adult form?"

Four shadows dropped to the ground, white eyes reduced to slits.

"Stay away from him," one of them said, raising his katana in a sure gesture.

The armored man shook the child, almost absent-mindedly.

"No? Well, then, this childish form will have to do."

The Shredder approached his gauntlet from Yoshi's neck. The tiny rat whined, all pretense gone. He was terrified.

Eyes still narrowed, the four turtles launched themselves at the Shredder in perfect harmony, each of their moves skillful and deadly, in a simultaneous attack where their respective weapons struck without getting in each other's way.

The leader of the Foot laughed and sent them flying in the air with ease.

"Do you truly believe that you can defeat me? Me, the Shredder?"

Leonardo groaned and picked himself up. His eyes met Yoshi's.

"I'm so-sorry," the small rat whispered, crying softly. "I only wan-wanted to find my brother."

Leonardo managed a smile.

"It's okay," he told him in a soothing tone. For once, the lie sounded convincing. "We'll get you out of here."

The Shredder laughed at him and squeezed Yoshi tighter. The rat let out a small cry. Raphael groaned and ran at him again, but the tall man kicked the turtle with a disdainful groan. Michelangelo launched his kusarigama at his head, and the Shredder seized the chain between two fingers and threw the shortest of the turtles against the opposite wall.

Leonardo clenched his fists. They stood no chance against the Shredder in a fair fight. They needed an idea. What could they do to save their father?

Their father who had put himself in great danger because he was concerned for his brother, and they, his sons, had been unable to prevent that.

He had wanted his brother so badly…

And then, it clicked. It was desperate, and completely silly, but it could work, and that was enough for Leonardo. The blue-masked turtle turned to Donatello.

"Donnie!" He whispered urgently. "Use the Kraang device!"

"Leo, I don't know how to reverse Splinter's state!" Donatello whispered back. "I have it powered again, but I still need to…"

Leonardo shook his head to cut him off.

"Not on Splinter! On Shredder!"

Donatello blinked.

"Oooh," he said. "I see. Well…"

The genius stuck his tongue out a little and manipulated the Kraang device like he had done that first time in the dojo, two days ago. He had no idea what move had what effect, but he had an excellent memory and remembered the sequence.

"What are you doing, turtles?" Shredder shouted in a deep, manly voice.

There was a loud buzz and a puff of pink smoke.

"Where am I?" A high-pitched, childish and muffled voice said. "Who are you?"

Karai, who had been watching the scene with amusement until then, froze. She gaped, unable to utter a single sound.

A tiny Shredder stood floating in his armor, with the Kuro Kabuto – his beloved helmet – hiding his entire head. Sitting next to him on the floor where he had been dropped, Yoshi was rubbing his bottom. Leonardo dashed to the child and took him in his arms, hugging him protectively. The boy sniffled.

"Donnie, this thing is awesome," Michelangelo said groggily, standing up. "It needs a name. I'm going to call it… The Kraanjuvenator!"

Tiny Shredder threw the helmet away, clenched his fists and stomped.

"Tell me what happened! You can't treat me like this! I am Hamato Saki, from the Hamato clan, and my family will destroy you!"

Now it was the turtles' turn to gape.

" _Hamato_ Saki?" Raphael whispered, disgusted.

"Brother?" Yoshi whispered with hope. "Brother!"

He jumped out of a startled Leonardo's arms and ran to the other child. When he reached him, he hugged him with strength.

"Brother! I knew I would find you!"

"Yoshi?" Saki said, returning the hug. "Yoshi, is that you? Why are you a rat? And who are these guys?"

Karai came back to her senses.

"What have you done, turtles?" She spat. "You'll pay for this! Foot, capture them!"

From the shadows around them, Foot soldiers advanced towards the mutants, various weapons in their hands.

"No problem," Raphael shouted defiantly, "these ones are in our league."

While the turtles began fighting, Yoshi placed himself in front of Saki, clearly intending to protect him. A Foot ninja grabbed his arm.

"Don't you dare touch my brother!" Saki shouted at the top of his voice, kicking the ninja between his legs.

The Foot ninja yelped and released Yoshi's arm. The other Foot hesitated. A master was a master, no matter his size or age.

"No!" Karai ordered. "Don't listen to him! Grab the rat!"

Leonardo took advantage of her distraction to kick her mid-stomach. She bent over, in pain.

"Yoshi, come with us!" Leonardo shouted. "It's time to go!"

"No!" Yoshi answered, shaking his head vehemently. "I'm staying with my brother! I…"

The mutant rat suddenly froze and let out a pained cry. Donatello, who was the closest, ran to him. He embraced the boy…

And suddenly found himself encircling his tall father's waist.

"Master Splinter?" He choked.

"Master Splinter!" His three brothers chorused.

"No!" Karai shouted.

"Yo-Yoshi?" Tiny Shredder asked in surprise.

Splinter looked disoriented.

"What… happened?"

"The effect just wears off?" Donatello said in disbelief, releasing his father to take a better look at him. "I've been trying to figure this out for hours and the effect just wears off?"

"Are you complaining, Donnie?" Raphael asked, relief obvious in his voice.

"No… Yes! A bit?"

"Let's go!" Leonardo said, happier than he had felt since Splinter had been turned into a child. "Sensei, we'll explain everything later!"

Splinter nodded and shrugged off badly advised Foot ninja who were trying to attack him. The five mutants made their way to the windows. Behind them, an upset Saki was shouting.

"Where is my brother Yoshi? I want to be with my brother Yoshi!"

Leonardo turned around and flashed a smug smile at Karai.

"Good luck with him, Karai. See you around!"

He didn't understand Karai's shouted reply – he was already outside, fading into the night with his whole family – but he could have sworn that the window panes had trembled.

"I'm not sure it'll help our relationship with her," Raphael remarked, his tone light.

"Nope," Leonardo answered, bumping fists with his brother. "I don't think it will."


	7. Epilogue

**Epilogue**

* * *

"Hmm. It looks like I have been quite busy these past two days."

Splinter stroked his whiskers while looking at his four sons. They had just related their crazy story, and were looking at him with eager expressions, as if they couldn't believe he was there.

"Indeed!" Michelangelo nodded. "You bit Leo… You kicked me… You insulted Raph… You ran away, twice… You plotted against us…"

The orange-masked turtle was swinging back and forth and counting each misdeed on his fingers, obviously impressed. Splinter chuckled.

"Yes. I was quite a troublemaker when I was young."

"And you corrected Leo's kata," Raphael added with great satisfaction. "That part was fun."

"Speak for yourself," Leonardo muttered, crossing his arms. "I was doing it right!"

There was a hint of concern in his voice, though, and Splinter shook his head fondly.

"I have no doubt, Leonardo. But the kata I taught you aren't entirely traditional. I adapted them to your turtle bodies."

"Sensei, don't you remember what happened?" Donatello asked, curious.

Splinter considered this question. He did remember, vague memories that floated at the edge of his consciousness. Including very embarrassing situations, and a forbidden skateboarding party that his reasonable, adult self couldn't admit having enjoyed.

"No," Splinter lied, his features as serene as ever.

His four sons sighed with obvious relief, exchanging not very discreet glances, and Splinter inwardly chuckled.

"So we're done, then?" Raphael asked happily. "No more turning-into-children nonsense?"

"I still have to figure out how the Kraang device…"

"…The _Kraanjuvenator_ ," Michelangelo interjected.

"…The Kraanjuvenator works," Donatello said. "I want to know if there was an emergency reverse functionality or not. I feel cheated."

His brothers rolled their eyes.

"You may," Splinter said, "but be careful, my son."

Donatello nodded.

"At worst, we'll only have to wait for two days," Leonardo remarked.

Raphael smirked.

"I bet Karai is having the time of her life with Tiny Shredder."

Michelangelo looked thoughtful.

"Is it bad that I feel sorry for the guy? He seemed like a decent child. I mean, he did kick that Foot ninja."

"He's a freaking murderer," Raphael spat.

"Raphael," Splinter admonished him before turning to his shortest son. "It's not bad, Michelangelo. As you know, Saki and I were very close as children. He was my best friend. We shared everything…"

The ninja master fell silent and gazed into the distance. Saki had been a trusting, loyal child. But everything had changed when he had grown up. He had never accepted Tang Shen's feelings for Yoshi… And then he had learned the truth about his past…

Splinter could only guess what a shock it had been. Learning that the father who had loved and raised him was, in fact, the murderer of his biological father…

 _He's reproducing the same pattern with Miwa,_ the giant rat realized. _Does the cycle of violence never end?_

His sons were still looking at him, expecting him to end his sentence.

"He was my brother," Splinter said. "He chose his own path, a path that broke our bonds."

The turtles waited for more, but Splinter added nothing.

"Well, nothing will break _our_ bonds," Raphael said fiercely. "Turtles first, right guys?"

As Leonardo, Donatello and Michelangelo agreed with enthusiasm, Splinter allowed himself to hope. Maybe his sons' generation would be wiser than the previous ones.

"And now that everything is settled," Raphael added with a grin, "I believe we were about to have a movie night."

* * *

In the Foot headquarters, a very tired and exasperated Karai was holding a spoon in front of Tiny Shredder's mouth.

"Fa- Saki," she began. "Please. You have to eat something."

"Master Saki," Saki pouted. "I told you, it's _Master_ Saki to you. Where is Yoshi? I want my brother!"

"Master Saki, your brother Yoshi…"

" _Master_ Yoshi!"

Karai grimaced as if the words were burning her tongue.

"Your brother _Master_ Yoshi isn't there. But I'm sure the ninja I sent will find him soon. Now will you please take your meal?"

Saki looked at her suspiciously. She wasn't telling him everything, he knew it. But he was beginning to get really hungry, and he took the spoon she offered. He didn't miss her relieved expression.

"Thank you, Karai," he said with his sweetest voice.

Let her believe that he trusted her. Soon, he would have his brother back.

He had a Plan.

 **The End**

* * *

 _Author's note: And this short story is complete! What Tiny Shredder's Plan is, or if and when Nanny Karai will snap, is entirely up to you._

 _Oh, and I am aware of the fact the Kraanjuvenator hasn't been destroyed. I wonder if Mikey will resist borrowing it to, let's say, test it on his brother Raph next time he'll try to punch him? And if Leo happened to be in the way, then the family would suddenly have two tiny problems on their hands._

 _But of course, it is mere speculation._


End file.
